Day 1: Simple Types

Lesson 6: Boolean

The boolean data type has a fancy name for a simple concept. Is something true or is it false?

1const iAmHuman = true;
2const theSunIsCold = false;

To really understand the power of this data type we need to look at Boolean Operators. These are like the addition +, subtraction -, division / and multiplication * operators you saw earlier but for this boolean data type. They are:

1let greaterThan = 4 > 3;
2let lessThan = 3 < 4;
3let greaterThanEqualTo = 4 >= 3;
4let lessThanEqualTo = 3 < 4;
5let equalTo = 3 == 3;
6let notEqualTo = 3 != 4;
7let exactlyEqualTo = 3 === 3;

All of the lines above will set the variable on the left of the first = sign to be true because the test that they apply is true. If we change the first line to let greaterThan = 1 > 3; then greaterThan will be set to false because the 1 is not greater than 3.

For not equal to != we simply take the equals to operator == and replace the first = with the not operator !.

Let's look at some more examples:

<h1>Hello World<h1>

const myAge = 35;
const yourAge = 28;
const imOlder = myAge > yourAge;
const sameAge = myAge === yourAge;
const imYounger = myAge < yourAge;
console.log(imOlder);
console.log(sameAge);
console.log(imYounger);

You can see in the console which test returns true and which returns false.

Use the playground below to practice a few other comparisons.

<h1>Hello World<h1>

const yourVariable = 100;
const myVariable = 101;
console.log(yourVariable < myVariable);

One last thing